The radial artery catheter was connected to the FloTrac TM transducer (Edwards Lifesciences, USA) coupled to both an anesthesia workstation (Primus Infinity Ⓡ Empowered, Dräger, Germany) and EV1000 TM (software version 1.5, Edwards Lifesciences) for hemodynamic measurements such as invasive blood pressure (IBP), SV, cardiac index (CI), and stroke volume variation (SVV). Before induction of anesthesia, a 20-G arterial catheter (Arterial cannula, Becton Dickinson Infusion Therapy System, USA) was inserted into the radial artery in the non-dominant hand after infiltration anesthesia with 2% lidocaine. Glycopyrrolate 0.2 mg was administered intravenously before transport to the operating theater. Patients fasted for 8-12 h before surgery and received maintenance fluids. The anesthetic regimen was standardized with total intravenous anesthesia for all patients. Each age group patients was randomly assigned by a computer-generated random number to one of three groups at preanesthetic visit according to the types of pneumatic compression of the lower extremities: Group 1 (control, no pneumatic compression), Group 2 (sequential pneumatic compression), and Group 3 (sustained pneumatic compression without decompression). Subjects were separated into those older than 65 years and those aged 65 years or younger initially. The patients that presented hypertension, cardiac arrhythmia, heart failure, vascular diseases, renal failure, CNS disorders, diabetes mellitus, alcohol or drug abuse, or a body mass index of 35 were excluded. One hundred and eighty patients, American Society of Anesthesiologists physical status I or II and aged 20 to 85 years, undergoing elective major operations that required invasive monitoring were enrolled. This prospective randomized controlled study was approved by the Institutional Review Board of author’s institution, and written informed consent was obtained for all participants.
Several types of pneumatic compression of the lower extremities, including pneumatic splint, intermittent compression, peristaltic compression, sequential compression, and military anti-shock trouser (MAST) are established interventions for various indications such as lymphedema, postthrombotic ulcers, arterial claudication, deep vein thrombosis, and severe trauma. Many previous reports have shown that the effects of pneumatic compression on the prevention of anesthesia- or position-related hypotension resulted from the peripheral redistribution of central blood volume. However, external compression of the lower extremities decreases the peripheral pooling of blood and augments venous return to increase central blood volume. Although Trendelenburg positioning or passive legraising is a simple maneuver to increase the blood in the central compartment to restore cardiac preload, it is not feasible in many clinical situations. Therefore, prevention of the redistribution of blood during anesthesia might be a good option to avoid hemodynamic instability and the adverse effects of intravenous fluids and cardiovascular active agents. Additionally, the administration of ephedrine has a risk of myocardial ischemia due to severe tachycardia. However, many previous reports have shown the risks of fluid overload although the role of perioperative fluid management remains under debate. In clinical practice, large volumes of fluid or short-acting cardiovascular active agent such as ephedrine may be administered to counteract anesthesia-induced hypotension.
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